1. Field of the Invention
The present invention relates to a control technology of a communication apparatus to perform telephone communication via a public network and telephone communication via the Internet.
2. Description of the Related Art
In recent years, the Internet is rapidly spreading worldwide. Communication devices using the Internet are proposed in various forms. Particular attention is paid to Internet phones and IP phones because they are expected to remarkably decrease communication charges.
An IP phone requires IP connection between users who want to communicate with each other. For this purpose, a rendezvous server is provided on the Internet. A telephone call is established as follows. The rendezvous server is provided with a table that maintains correspondence between telephone numbers and nearby Internet service providers. A receiving user is notified of a call request and an originating user's IP address via the public network. Both users are simultaneously connected via the rendezvous server to thereby establish speech communication.
The Internet phone is used in two modes: dial-up connection via Internet service providers and continuous and direct interconnection (that is, always-on connection) via a LAN.
When the former mode is used for dial-up connection via an Internet service provider, the Internet service provider permits a terminal equipment to make a PPP-connection to the Internet only when a connection request occurs. Accordingly, a normal Internet procedure cannot directly call an individual who makes a dial-up connection via an Internet service provider.
The former is based on dial-up connection, uses the PSTN line to connect to a provider, and then uses a data modem for connection. Therefore, call signals and control data cannot be used independently, thus occupying the communication line. As a result, this mode has made it impossible to use two lines simultaneously by changing between the PSTN phone and the IP phone using a single terminal equipment.
On the other hand, the latter mode, i.e., the continuous and direct interconnection via a LAN has come into practical use as an original IP phone using a speech coding/decoding function, a network processor having call connection processing, and the like. Many proposals for IP phones concern methods of interconnecting terminal equipments that are continuously connected to the Internet. A complicated configuration may be needed for the use of telephones. For example, an ordinary analog telephone set needs to be connected to a splitter. Further, a DSL modem needs to connect with a terminal equipment connectable to the LAN.
There has not been proposed a technique that can realize the use of two lines, i.e., the continuous connection line (or always-on connection) and the PSTN line with a simple configuration. Such dual terminal equipment is especially necessary for a situation where there is a plurality of types of public networks.